On Wed, Jun 17, 2009 at 8:39 AM, Pallipadi, Venkatesh<venkatesh.pallipadi@xxxxxxxxx> wrote: > On Thu, Jun 11, 2009 at 08:23:29AM -0700, Mathieu Desnoyers wrote: >> * Simon Holm Thøgersen (odie@xxxxxxxxx) wrote: >> > man, 08 06 2009 kl. 10:32 -0400, skrev Dave Jones: >> > > On Mon, Jun 08, 2009 at 08:48:45AM -0400, Mathieu Desnoyers wrote: >> > > >> > > > > > >> Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=13475 >> > > > > > >> Subject : suspend/hibernate lockdep warning >> > > > > > >> References : http://marc.info/?l=linux-kernel&m=124393723321241&w=4 >> > > > > > >> > > > > > I suspect the following commit, after revert this patch I test 5 times >> > > > > > without lockdep warnings. >> > > > > > >> > > > > > commit b14893a62c73af0eca414cfed505b8c09efc613c >> > > > > > Author: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> >> > > > > > Date: Sun May 17 10:30:45 2009 -0400 >> > > > > > >> > > > > > [CPUFREQ] fix timer teardown in ondemand governor >> > > > > >> > > > > The patch is probably not at fault here. I suspect it's some latent bug >> > > > > that simply got exposed by the change to cancel_delayed_work_sync(). In >> > > > > any case, Mathieu, can you take a look at this please? >> > > > >> > > > Yes, it's been looked at and discussed on the cpufreq ML. The short >> > > > answer is that they plan to re-engineer cpufreq and remove the policy >> > > > rwlock taken around almost every operations at the cpufreq level. >> > > > >> > > > The short-term solution, which is recognised as ugly, would be do to the >> > > > following before doing the cancel_delayed_work_sync() : >> > > > >> > > > unlock policy rwlock write lock >> > > > >> > > > lock policy rwlock write lock >> > > > >> > > > It basically works because this rwlock is unneeded for teardown, hence >> > > > the future re-work planned. >> > > > >> > > > I'm sorry I cannot prepare a patch current... I've got quite a few pages >> > > > of Ph.D. thesis due for the beginning of July. >> > > >> > > I'm kinda scared to touch this code at all for .30 due to the number of >> > > unexpected gotchas we seem to run into every time we touch something >> > > locking related. So I'm inclined to just live with the lockdep warning >> > > for .30, and see how the real fixes look for .31, and push them back >> > > as -stable updates if they work out. >> > >> > Unfortunately I don't think it is just theoretical, I've actually hit >> > the following (that haven't got anything to do with suspend/hibernate) >> > >> > INFO: task cpufreqd:4676 blocked for more than 120 seconds. >> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> > cpufreqd D eee2ac60 0 4676 1 >> > ee01bd68 00000086 eee2aad0 eee2ac60 00000533 eee2aad0 eee2ac60 0002b16f >> > 00000000 eee2ac60 7fffffff 7fffffff eee2ac60 7fffffff 7fffffff 00000000 >> > ee01bd70 c03117ee ee01bdbc c0311c0c eee2aad0 eecf6900 eee2aad0 eecf6900 >> > Call Trace: >> > [<c03117ee>] schedule+0x12/0x24 >> > [<c0311c0c>] schedule_timeout+0x17/0x170 >> > [<c011a4f7>] ? __wake_up+0x2b/0x51 >> > [<c0311afd>] wait_for_common+0xc4/0x135 >> > [<c011a694>] ? default_wake_function+0x0/0xd >> > [<c0311be0>] wait_for_completion+0x12/0x14 >> > [<c012bc6a>] __cancel_work_timer+0xfe/0x129 >> > [<c012b635>] ? wq_barrier_func+0x0/0xd >> > [<c012bca0>] cancel_delayed_work_sync+0xb/0xd >> > [<f20948f9>] cpufreq_governor_dbs+0x22e/0x291 [cpufreq_ondemand] >> > [<c02af857>] __cpufreq_governor+0x65/0x9d >> > [<c02af960>] __cpufreq_set_policy+0xd1/0x11f >> > [<c02b02ae>] store_scaling_governor+0x18a/0x1b2 >> > [<c02b09a5>] ? handle_update+0x0/0xd >> > [<c02b0124>] ? store_scaling_governor+0x0/0x1b2 >> > [<c02b08c9>] store+0x48/0x61 >> > [<c01acbf4>] sysfs_write_file+0xb4/0xdf >> > [<c01acb40>] ? sysfs_write_file+0x0/0xdf >> > [<c0175535>] vfs_write+0x8a/0x104 >> > [<c0175648>] sys_write+0x3b/0x60 >> > [<c0103110>] sysenter_do_call+0x12/0x2c >> > INFO: task kondemand/0:4956 blocked for more than 120 seconds. >> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> > kondemand/0 D 00000533 0 4956 2 >> > ee1d9efc 00000046 c011815f 00000533 071148de ee1e0080 ee1e0210 00000000 >> > c03ff478 9189e633 00000082 c03ff478 ee1e0210 c04159f4 c04159f0 00000000 >> > ee1d9f04 c03117ee ee1d9f28 c0313104 ee1d9f30 c04159f4 ee1e0080 c01183be >> > Call Trace: >> > [<c011815f>] ? update_curr+0x6c/0x14b >> > [<c03117ee>] schedule+0x12/0x24 >> > [<c0313104>] rwsem_down_failed_common+0x150/0x16e >> > [<c01183be>] ? dequeue_task_fair+0x51/0x56 >> > [<c031313d>] rwsem_down_write_failed+0x1b/0x23 >> > [<c031317e>] call_rwsem_down_write_failed+0x6/0x8 >> > [<c03125dd>] ? down_write+0x14/0x16 >> > [<c02b0460>] lock_policy_rwsem_write+0x1d/0x33 >> > [<f20944aa>] do_dbs_timer+0x45/0x266 [cpufreq_ondemand] >> > [<c012b8f7>] worker_thread+0x165/0x212 >> > [<f2094465>] ? do_dbs_timer+0x0/0x266 [cpufreq_ondemand] >> > [<c012e639>] ? autoremove_wake_function+0x0/0x33 >> > [<c012b792>] ? worker_thread+0x0/0x212 >> > [<c012e278>] kthread+0x42/0x67 >> > [<c012e236>] ? kthread+0x0/0x67 >> > [<c01038eb>] kernel_thread_helper+0x7/0x10 >> > >> > I've only seen it once in 5 boots and CONFIG_PROVELOCKING does not give any >> > warnings about this, though it does yell when switching governor as reported >> > by others in bug #13493. >> > >> > Let's hope Mathieu nails it, though I know he's busy with his thesis. >> > >> >> Thanks for the lockdep reports, >> >> I'm currently looking into it, and it's not pretty. Basically we have : >> >> A >> B >> (means B nested in A) >> >> work >> read rwlock policy >> >> dbs_mutex >> work >> read rwlock policy >> >> write rwlock policy >> dbs_mutex >> >> So the added dbs_mutex <- work <- rwlock policy dependency (for proper >> teardown) is firing the reverse dependency between policy rwlock and >> dbs_mutex. >> >> The real way to fix this is to do not take the rwlock policy around >> non-policy-related actions, like governor START/STOP doing worker >> creation/teardown. >> >> One simple short-term solution would be to take a mutex outside of the >> policy rwlock write lock in cpufreq.c. This mutex would be the >> equivalent of dbs_mutex "lifted" outside of the rwlock write lock. For >> teardown, we only need to hold this mutex, not the rwlock write lock. >> Then we can remove the dbs_mutex from the governors. >> >> But looking at cpufreq.c's cpufreq_add_dev() is very much like kicking a >> wasp nest: a lot of error paths are not handled properly, and I fear >> someone will have to go through the code, fix the currently incorrect >> code paths, and then add the lifted mutex. >> >> I currently have no time for implementation due to my thesis, but I'll >> be happy to review a patch. >> > > How about below patch on top of Mathieu's patch here > http://marc.info/?l=linux-kernel&m=124448150529838&w=2 > > [PATCH] cpufreq: Eliminate lockdep issue with dbs_mutex and policy_rwsem > > This removes the unneeded dependency of > write rwlock policy > dbs_mutex > > dbs_mutex does not have anything to do with timer_init and timer_exit. It > is just to protect dbs tunables in sysfs cpufreq/ondemand and is not > needed to be held during timer init, exit as well as during governor limit > changes. > > Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx> > --- > drivers/cpufreq/cpufreq_ondemand.c | 8 +++----- > 1 files changed, 3 insertions(+), 5 deletions(-) latest linux-2.6 git + this patch, hibernate test result: [ 221.956815] [ 221.956817] ======================================================= [ 221.957017] [ INFO: possible circular locking dependency detected ] [ 221.957173] 2.6.30-06692-g3fe0344-dirty #77 [ 221.957276] ------------------------------------------------------- [ 221.957431] 94cpufreq/1914 is trying to acquire lock: [ 221.957561] (&(&dbs_info->work)->work){+.+...}, at: [<c1037f46>] __cancel_work_timer+0x8c/0x18c [ 221.958034] [ 221.958036] but task is already holding lock: [ 221.958336] (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<c1284528>] lock_policy_rwsem_write+0x33/0x5b [ 221.958850] [ 221.958852] which lock already depends on the new lock. [ 221.958855] [ 221.959258] [ 221.959260] the existing dependency chain (in reverse order) is: [ 221.959625] [ 221.959627] -> #1 (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}: [ 221.959994] [<c1049d0f>] __lock_acquire+0x91e/0xaa9 [ 221.959994] [<c1049f35>] lock_acquire+0x9b/0xbe [ 221.959994] [<c1335fed>] down_write+0x2f/0x4b [ 221.959994] [<c1284528>] lock_policy_rwsem_write+0x33/0x5b [ 221.959994] [<c1286097>] do_dbs_timer+0x45/0x23b [ 221.959994] [<c103851e>] worker_thread+0x170/0x23c [ 221.959994] [<c103ad8b>] kthread+0x45/0x6e [ 221.959994] [<c1003dc7>] kernel_thread_helper+0x7/0x10 [ 221.959994] [<ffffffff>] 0xffffffff [ 221.959994] [ 221.959994] -> #0 (&(&dbs_info->work)->work){+.+...}: [ 221.959994] [<c1049c1f>] __lock_acquire+0x82e/0xaa9 [ 221.959994] [<c1049f35>] lock_acquire+0x9b/0xbe [ 221.959994] [<c1037f71>] __cancel_work_timer+0xb7/0x18c [ 221.959994] [<c1038051>] cancel_delayed_work_sync+0xb/0xd [ 221.959994] [<c1286484>] cpufreq_governor_dbs+0x1f7/0x263 [ 221.959994] [<c1283b13>] __cpufreq_governor+0x66/0x9d [ 221.959994] [<c1283c89>] __cpufreq_set_policy+0x13f/0x1c3 [ 221.959994] [<c1284151>] store_scaling_governor+0x159/0x188 [ 221.959994] [<c1284d12>] store+0x42/0x5b [ 221.959994] [<c10d783d>] sysfs_write_file+0xb8/0xe3 [ 221.959994] [<c109937e>] vfs_write+0x82/0xdc [ 221.959994] [<c109946d>] sys_write+0x3b/0x5d [ 221.959994] [<c100331d>] syscall_call+0x7/0xb [ 221.959994] [<ffffffff>] 0xffffffff [ 221.959994] [ 221.959994] other info that might help us debug this: [ 221.959994] [ 221.959994] 2 locks held by 94cpufreq/1914: [ 221.959994] #0: (&buffer->mutex){+.+.+.}, at: [<c10d77aa>] sysfs_write_file+0x25/0xe3 [ 221.959994] #1: (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<c1284528>] lock_policy_rwsem_write+0x33/0x5b [ 221.959994] [ 221.959994] stack backtrace: [ 221.959994] Pid: 1914, comm: 94cpufreq Not tainted 2.6.30-06692-g3fe0344-dirty #77 [ 221.959994] Call Trace: [ 221.959994] [<c1048895>] print_circular_bug_tail+0x5d/0x68 [ 221.959994] [<c1049c1f>] __lock_acquire+0x82e/0xaa9 [ 221.959994] [<c1048415>] ? mark_lock+0x1e/0x1c7 [ 221.959994] [<c1049f35>] lock_acquire+0x9b/0xbe [ 221.959994] [<c1037f46>] ? __cancel_work_timer+0x8c/0x18c [ 221.959994] [<c1037f71>] __cancel_work_timer+0xb7/0x18c [ 221.959994] [<c1037f46>] ? __cancel_work_timer+0x8c/0x18c [ 221.959994] [<c1048601>] ? mark_held_locks+0x43/0x5b [ 221.959994] [<c1335972>] ? __mutex_unlock_slowpath+0xf1/0x101 [ 221.959994] [<c104876a>] ? trace_hardirqs_on+0xb/0xd [ 221.959994] [<c1038051>] cancel_delayed_work_sync+0xb/0xd [ 221.959994] [<c1286484>] cpufreq_governor_dbs+0x1f7/0x263 [ 221.959994] [<c103e02b>] ? up_read+0x16/0x29 [ 221.959994] [<c1283b13>] __cpufreq_governor+0x66/0x9d [ 221.959994] [<c1283c89>] __cpufreq_set_policy+0x13f/0x1c3 [ 221.959994] [<c1283ff8>] ? store_scaling_governor+0x0/0x188 [ 221.959994] [<c1284151>] store_scaling_governor+0x159/0x188 [ 221.959994] [<c1284659>] ? handle_update+0x0/0x28 [ 221.959994] [<c1284528>] ? lock_policy_rwsem_write+0x33/0x5b [ 221.959994] [<c1283ff8>] ? store_scaling_governor+0x0/0x188 [ 221.959994] [<c1284d12>] store+0x42/0x5b [ 221.959994] [<c10d783d>] sysfs_write_file+0xb8/0xe3 [ 221.959994] [<c109937e>] vfs_write+0x82/0xdc [ 221.959994] [<c10d7785>] ? sysfs_write_file+0x0/0xe3 [ 221.959994] [<c109946d>] sys_write+0x3b/0x5d [ 221.959994] [<c100331d>] syscall_call+0x7/0xb [ 222.336101] PM: Marking nosave pages: 000000000009f000 - 0000000000100000 [ 222.340205] PM: Basic memory bitmaps created [ 222.344226] PM: Syncing filesystems ... done. > > diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c > index e741c33..1c94ff5 100644 > --- a/drivers/cpufreq/cpufreq_ondemand.c > +++ b/drivers/cpufreq/cpufreq_ondemand.c > @@ -352,8 +352,8 @@ static ssize_t store_powersave_bias(struct cpufreq_policy *unused, > > mutex_lock(&dbs_mutex); > dbs_tuners_ins.powersave_bias = input; > - ondemand_powersave_bias_init(); > mutex_unlock(&dbs_mutex); > + ondemand_powersave_bias_init(); > > return count; > } > @@ -626,14 +626,14 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, > > dbs_tuners_ins.sampling_rate = def_sampling_rate; > } > + mutex_unlock(&dbs_mutex); > dbs_timer_init(this_dbs_info); > > - mutex_unlock(&dbs_mutex); > break; > > case CPUFREQ_GOV_STOP: > - mutex_lock(&dbs_mutex); > dbs_timer_exit(this_dbs_info); > + mutex_lock(&dbs_mutex); > sysfs_remove_group(&policy->kobj, &dbs_attr_group); > dbs_enable--; > mutex_unlock(&dbs_mutex); > @@ -641,14 +641,12 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, > break; > > case CPUFREQ_GOV_LIMITS: > - mutex_lock(&dbs_mutex); > if (policy->max < this_dbs_info->cur_policy->cur) > __cpufreq_driver_target(this_dbs_info->cur_policy, > policy->max, CPUFREQ_RELATION_H); > else if (policy->min > this_dbs_info->cur_policy->cur) > __cpufreq_driver_target(this_dbs_info->cur_policy, > policy->min, CPUFREQ_RELATION_L); > - mutex_unlock(&dbs_mutex); > break; > } > return 0; > -- > 1.6.0.6 > > -- Regards dave -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
